Marine ply in shower

[Jimmy Doc]

Hi all, I'm about to start a bathroom and the client has knocked down a wall to make room for a shower, there is now two stud Walls in shower cubicle with marine ply and one wall sand/cement, there is no shower tray screed floor, what prep work needs to be done here and what addy is to be used

[Bri]

Change the ply for a cement/ marmox type board, tank the shower area then tile using a single part, flexible adhesive (powdered, cement based in the bags).

[nybor62]

im with brian on this

[Mike]

are you fitting a shower base or forming a wetroom floor?

[deanotile]

remove the ply and replace with tile backer board
BS 5385 3.2.4.2
The use of sheets and boards that are subject to movement from changes in moisture content, e.g. wood-based materials such as plywood, chipboard, wood particle boards, etc. should be avoided if at all possible. If such boards have to be used they should be restricted to small areas and tiles should not bridge joints between boards. It is good practice to seal all exposed edges and the backs, but not the faces, of such boards with a suitable sealer to prevent distortion by atmospheric humidity changes. Care should be taken to ensure such boards are not installed in a condition where their moisture content is higher than the ambient equilibrium moisture content once the tiled installation is in use. Failure to observe this can lead to subsequent warping and distortion of the boards with consequent cracking and delamination of the tiling.

[Jimmy Doc]

Thanks, I doubt client will change marine ply as he's fixed it, I'll say to him though, if it's not being changed can you tank over marine ply, does the addy need to be flexible and water resistant, does tanking need to be primed before tiling,where would u get this marmox board

[deanotile]

personally i would not ask the customer i would tell them. but if you decide to do it find out from the manufacturers of the tanking if it is OK to do.

[whitebeam]

If he won't replace ply, As Deano says and tank 100% with flexible adhesive and grout...

No need to prime tanking

[Jimmy Doc]

Thanks, if it's all tanked and sealed is the ply not completely waterproofed? Where would I find suitable boards for the job,

[deanotile]

is the ply sealed on the edges and the back?

[Jimmy Doc]

I'm not sure, what would it need to be sealed with, does what about face side

[deanotile]

remove the ply and replace with tile backer board
BS 5385 3.2.4.2
The use of sheets and boards that are subject to movement from changes in moisture content, e.g. wood-based materials such as plywood, chipboard, wood particle boards, etc. should be avoided if at all possible. If such boards have to be used they should be restricted to small areas and tiles should not bridge joints between boards. It is good practice to seal all exposed edges and the backs, but not the faces, of such boards with a suitable sealer to prevent distortion by atmospheric humidity changes. Care should be taken to ensure such boards are not installed in a condition where their moisture content is higher than the ambient equilibrium moisture content once the tiled installation is in use. Failure to observe this can lead to subsequent warping and distortion of the boards with consequent cracking and delamination of the tiling.

back and edges but i do not know how it will be affected with a tanking system so as i said above speak to the manufacturer.

[Jimmy Doc]

I will ring manufacturer tomorrow denotive, what kind of sealer will be needed for edges and back of ply